A typical CATV network provides many content selections to a subscriber's media device by way of a single electrically conductive cable that provides a signal stream to the media device. A typical CATV or cable television network includes a head end facility from which a plurality of feeder cable lines emanate. The feeder cable lines branch off at a tap having ports. A drop cable, which may be a single coaxial cable, extends from each port to a respective user unit, or user. The CATV system is a two-way communication system. A downstream bandwidth carries signals from the head end to a user and an upstream bandwidth carries upstream signals from the user to the head end.
One example of such a system is a bidirectional CATV system with a head end controlled by a system operator and with a plurality of users' televisions equipped with set top boxes or cable modems. Downstream bandwidth of the CATV system may include broadcast television channels, video on demand services, internet data, home security services, and voice over internet (VoIP) services. Upstream bandwidth may include data related to video on demand, internet access, security monitoring, or other services provided by the system operator. In one possible configuration, the upstream and downstream bandwidths are transmitted between the head end and the tap via optical fiber, and between the tap and the user via coaxial cable. Upstream and downstream bandwidths are typically transmitted via oscillatory electrical signals propagated along the cable lines in a discrete frequency range, or channel, that is distinct from the frequency ranges of other content selections. Downstream bandwidth frequencies typically range from 50-1,000 megahertz (MHz), and upstream bandwidth frequencies typically range from 7-49 MHz.
Each drop cable entering a user's dwelling usually enters a splitter having multiple outlet ports. Distribution cables connected to the outlet ports route the signals to various rooms, often terminating at a wall jack. In many installations, the distribution cable is split again, depending on component setup. The network of distribution cables, splitters, and distribution points is referred to as a drop system. Within the drop system, not every port on a splitter may be utilized, and not every wall jack within a structure may have a device connected to it.
One problem with the un-terminated splitters and wall jacks is that users unwittingly allow a significant level of radio frequency noise, or ingress noise, to enter the network and be passed along the upstream bandwidth. Unbeknownst to most users, the exposed port in a splitter or wall jack acts as an antenna, collecting radio frequency noise from sources such as electrical devices with alternating electrical currents. Examples of electrical devices that create radio frequency noise include garbage disposals, vacuum cleaners, microwave ovens, etc. Commonly used devices transmitting signals in the radio frequency range may also contribute to the ingress noise picked up by the exposed port in a splitter or wall jack and transmitted through the upstream bandwidth. Such devices include cell phones, wireless networks, baby monitors, and the like.
Radio frequency noise may also enter the upstream bandwidth of a CATV system if a connector is loose or cracked, if the coaxial cable is damaged, or if there is a malfunctioning user device in the drop system. As used herein, the term “ingress noise” means all such sources of radio frequency noise and includes (but is not limited to) open ports, loose connectors, un-terminated splitters, and poor performing splitters.
The ingress noise passing from each user to the upstream bandwidth “funnels” at the tap, where it is combined with ingress noise from other users. The additive effect of ingress noise passing from hundreds or thousands of users to the upstream bandwidth is a serious problem plaguing the cable television industry. Unlike noise accumulated in the downstream bandwidth, which manifests itself as progressively deteriorating picture quality, ingress noise in the upstream bandwidth may not be detected until communication breaks down completely or, in the case of spread spectrum technology, drastically slows down network performance. Experts estimate that approximately 95 percent of ingress noise originates from the drop system, including the user dwelling. Oliver, Kevin J. “Preventing Ingress in the Return Path.” CedMagazine.com. Oct. 1, 1996. <http://cedmagazine.com/preventing-ingress-in-the-return.aspx>. Unfortunately, the cable television industry has little control of the drop system architecture within a user dwelling. The drop system is the least accessible and least controllable portion of the CATV network. Thus, any attempt to properly terminate the exposed ports and wall jacks would probably be futile.